Hearing

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Hearing is a complex sensory process that transforms sound waves into electrical signals interpretable by the brain. This sensory ability enables us to communicate effectively, enjoy music, and remain aware of our surroundings. The process involves intricate mechanical and neural mechanisms working together seamlessly.
Sound waves from the environment are first captured and funneled by the external ear into the external acoustic meatus. These waves are then transformed into mechanical vibrations by the tympanic membrane and ossicles of the middle ear. In the cochlea, mechanical energy is converted into electrical signals that travel along the cochlear nerve to the brain for interpretation.
The auditory system not only processes sound but also protects delicate structures from potential damage caused by loud noises. Additionally, it allows us to localize sounds and distinguish between subtle variations in frequency and intensity, critical for understanding speech and enjoying complex auditory inputs like music.

Watch the video below to explore how sound waves travel through the ear, are transformed into neural signals, and are processed in the brain to create rich auditory experiences.

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Sound conduction

Sound transduction

Hair cells in the spiral organ (of Cort)i of the cochlea convert mechanical vibrations into electrical signals. Fluid waves in the cochlea stimulate the basilar membrane, bending the stereocilia on hair cells and opening ion channels. This results in depolarization and neurotransmitter release, initiating action potentials in the cochlear nerve.

Loudness, pitch and frequency

Hearing depends on how the ear processes loudness, pitch, and frequency of sound waves. Loudness is determined by the amplitude of sound waves, with higher amplitudes creating stronger vibrations in the cochlea, leading to louder perceptions. Pitch depends on frequency, measured in hertz (Hz), with low-frequency waves producing low-pitched sounds and high-frequency waves creating high-pitched sounds. The basilar membrane in the cochlea plays a key role in frequency detection—its stiff base responds to high frequencies, while its flexible apex detects low frequencies. These mechanical signals are converted into electrical impulses by hair cells, allowing the brain to perceive and interpret sound.

Auditory pathway

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Reinforce your learning with our interactive quiz on the physiology of hearing. Test your knowledge of sound conduction, transduction, and the auditory pathway.

Summary